Asymmetric division is a fundamental process that generates daughter cells with different developmental fates. Formation of the germline during embryogenesis in C. elegans offers an ideal system in which to study this process. The germline is generated via a series of asymmetric divisions that require the MES-1 protein. MES-1, a receptor tyrosine kinase-like protein, functions as an orientation cue for these events and is itself asymmetrically localized. It is localized to a region of the germline cell that borders the gut cell and where the next germline cell will form. Aim 1 will investigate the role of cell-cell contact in localizing MES-1 and polarizing the events that occur during germline development. Individual cells of the embryo will be separated and reassociated to test if these interactions are required. MES-1 and other asymmetrically positioned cell components will be visualized by immunofluorescence to see if their pattern is altered in cells that develop in isolation. Aim 2 will determine which region of MES-1 is required for localization. Fusion proteins of portions of MES-1 and the green fluorescent protein (GFP) will be created and transformed into worms, where the position of these fusions will be assessed. The hypothesis predicts the extracellular region of MES-1 interacts with a ligand on the adjacent gut cell, which in turn causes it to accumulate at the boundary between the cells. Aim 3 will identify genes that participate with MES-1 and that function in these divisions. Genes will be screened by the technique of RNAi. Genes that cause defects indicative of their role in germline divisions will be pursued. This application may find that cell-cell contact is required for germline development, which would significantly alter the accepted view of early C. elegans embryogenesis. It has been thought that the germline divisions occur cell-autonomously. Thus these experiments may identify a new signaling pathway. Identification of other genes that function in this process will not only lay the foundation for future experiments but will also advance our understanding of asymmetric divisions.